1. Field of the Invention
The invention relates to a receiver for extended television signals in which a wide aspect ratio picture and at least one horizontal bar are jointly coded so as to form a standard aspect ratio picture. The horizontal bar is used to transmit "hidden" enhancement information which can be used by the extended television signal receiver to improve the vertical resolution of the wide aspect ratio television signal.
2. Description of the Related Art
European Patent Application EP-A-0,460,750 (PHN 13,359) discloses an extended television signal receiver of the above-mentioned type. The amplitude of the enhancement information in the horizontal bars is reduced to decrease the visibility of the enhancement information and to prevent the operation of current television receivers from being disturbed by the enhancement information. However, as a consequence of its reduced amplitude, the enhancement information is more susceptible to noise. When the extended television receiver adds noisy enhancement information to the wide aspect ratio picture to improve the vertical resolution thereof, the whole wide aspect ratio picture will be disturbed by noise.
Another problem is formed by the amplitude response distortion sensitivity of the combination of the wide aspect ratio picture and the enhancement information. The baseband enhancement spectrum corresponds directly to the luminance spectrum. However, in the encoder, the modulated enhancement signal is inverse spectrum vestigial sideband (VSB-) modulated on the color subcarrier. Thus, the original baseband enhancement spectrum has been inverted. In the extended television signal receiver, the modulated enhancement frequency component .omega..sub.sc -.omega. is demodulated, processed and added to frequency component .omega. of the luminance signal. Amplitude response distortions in the channel result in distorted mutual amplitude ratio's of corresponding luminanee/enhancement frequency components.